Process for rust-proofing metal.



. UNITED STATES WILLIAM H. ALLEN, OF, DETROIT, MICHIGAN, AS SIGNOIt TOPARKER, RUST-PROOF 0011- I PATENT o en;

DAM OF AMERICA, DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

rnocnss mnusr-rnoormo METAL.

No Drawing.

To all whom it may concern:

Be it known that I, WILLIAM H. ALLEN, a citizen of theUnited States,residing at Detroit, in the county of Wayne and State of Michigan, haveinvented a new and useful Process for Rust-Proofing Metal, of which thefollowing is a specification.

This invention relates to the process of so acting upon the surfaces ofarticles of .iron and steel as to render them rust-proof, that is, tosochange the chara'cter of such surfaces that they will besubstantiallyunaffected upon exposure to moist air. This invention iscarried out b changing such surfaces into insoluble basic phosphate ofiron byimmersing' the articles in a proper bath, hereinafter described,at substantially the boiling point, which surface will thereafter resistth'e'corroding action of the atmosphere.

Ferric phosphate may be prepared-in any well known manner, but I preferto add to a solution of a soluble phosphate, such as sodium phosphate, asolution of a ferric salt, such as ferric sulfate or chlorid, whichcauses a precipitation of ferric phosphate. The reaction maybe written z4) e+ s 4= v Fe, P0,) +3Na SO :Ihis precipitate is then washed to removethe soluble sodium salt. The ferric phosphate is then dissolved in phoshoric acid which results in the formation 0 ferric acid phosphate.

A substantially eight-tenths percent. so, lution of this ferric acidphosphate in Water is brought to about the boiling point and the Thesurfaces of the iron and steel become black as the basic phosphates ofiron are Specification of Letters Patent. 1 Patented'Feh13, 191'3',Application nieamvembe'r e, 1915. Serial No. 60,072.

formed, the actionof the bath being con-l tinued until hydrogen ceasesto escape, after which the articles are removed from the bath and arethen dried and oiled.

It will be noticed that no free phosphoric acid is introduced inthe'bath, which is a solution of a phosphate in salt. The affectf, edsurfaces of the iron or steel are integral with the body of the articleand after the treatment is completed there is no tendency of thesurfaces to separate from the main body of the article. The bath maybecon tinued in use until it is exhausted or be kept up to standardstrength through the addition of fresh ferric acid phosphate.

One of the prime advantages of this invention lies in the fact that theferric acid phosphate can be, shipped to the factories whererust-proofing is to be carried out,

Where it can be added to the bath as required, thus avoiding themistakes that are liable to occur where unskilled labor is employed tomix the ingredients of previous rust-proofing baths.

The exact composition of the ferric acid. phosphates is uncertain, asthese compounds I therefore do not wish to be understood as vouching forthe accuracies of the reactions given above.

-I claim 1. The process of rendering articles of iron and steel rust-proof which consists in immersing the samein a solution of ferric acidphosphate.

2. and steel rust-proof which. consists in immersin the same in asubstantiallyboiling he process of rendering articles of iron bath 6water containing about eight-tenths e;

per cent. of ferric acid phosphate.

tion.

In testi ony whereof I sign this specifica WILLIAM H. ALLEN.

